The present invention relates to instruments for measuring light pulses clocked at a high repetition rate in the same interval with the same waveform, and also to electron tube devices for measuring the light pulses.
The streaking camera is a device for monitoring the intensity of light changing with time at high speed.
The streaking tube used in each streaking camera is an electron tube which contains a pair of deflection electrodes located between the photocathode and the phosphor layer.
If light is incident on the photocathode of the streaking tube, the photocathode can emit photoelectrons. When an electric field is applied across a pair of deflection electrodes during motion of photoelectrons traveling from the photocathode to the phosphor layer, changes in brightness in the direction of the electron beam moving on the phosphor layer appear corresponding to changes in the incident light.
The tube to obtain changes in brightness is called the streaking tube.
The streaking camera consists of a streaking tube as described above, an optical system used to project incident light being measured onto the phosphor layer, and a power supply used to feed power to the streaking tube.
The streaking image on the phosphor layer, after being picked up by a television camera, can be analyzed by processing the video signal obtained by the television camera. When the streaking image of light pulses clocked at a high repetition rate is repetitively picked up for one field period of time, a superposed streaking image with a large amplitude can favorably be obtained.
The dark current inherent to the streaking tube is integrated during the scanning time, and this current makes measurement of brightness in the low intensity range inaccurate.
The data obtained has a limited contrast range due to the limited dynamic range of the built-in video signal amplifier, and no more excessive dynamic range can be expected.
An analysis of the streaking image of the light pulses clocked at a high repetition rate with a dynamic range of 10.sup.4 to 10.sup.8 is required, but it cannot be done by the conventional technique.
The above are the problems to be solved.
The first objective of the present invention is to present an instrument for analyzing the streaking image of light pulses clocked at a high repetition rate with an extended dynamic range realized by sensing the light pulses by using a photoelectron multiplier tube as a photoelectric conversion device.
The second objective of the present invention is to present another instrument for analyzing an arbitrarily selected portion of the streaking image of the light pulses clocked at a high repetition rate with an extended dynamic range realized by picking up the arbitrarily selected portion of the streaking image on the phosphor layer with a narrow-width stripe perpendicular to the time coordinate on the phosphor layer and then by multiplying the selected portion of the streaking image with a photoelectron multiplier tube.
The third objective of the present invention is to present a new type of electron tube device suitable for measuring light pulses of the same waveform clocked at an unchanged repetition rate with an extended dynamic range.